CHANGES OF SOY PROTEIN UNDER ULTRA-HIGH HYDRAULIC PRESSURE

High pressure (<500 MPa) was applied to soy milk and the protein chang es were examined. Soy milk remained a liquid within the range of exami ned pressures, although its viscosity increased when the time of press urization was less than 10 min. However, the soy milk changed from a l iquid to a sol after treatment at 500 MPa for 30 min. The liquid soy m ilk showed improved emulsifying activity and stability but reduced emu lsifying capacity. Sulfhydryl content of this soy milk was increased s lightly after anaerobic pressurization. Harder tofu could be made from pressurized soy milk with CaCl2 than could be made with unpressurized soy milk. Electrophoresis and isoelectrofocusing revealed that soy pr oteins were dissociated and some of them coagulated by high pressure. Fluorescence analysis also revealed that soy proteins were modified by high pressure to have larger hydrophobic regions. After pressure trea tment, soy milk showed a higher affinity for beany flavour components and saponins which would lead to better use of soy milk in soy foods.